This invention relates generally to optical communications, and more particularly, to a method of and apparatus for providing a 1xc3x97K integrated wavelength-selective cross connect for use in a wavelength division multiplex (WDM) network, where K is an integer representing the number of output paths.
At nodes in a wavelength division multiplex (WDM) network, it is often necessary to route each wavelength channel from a single incoming fiber independently to one of a plurality (K) of output paths. Some of these paths may terminate (or be dropped) independently into a receiver, and some may continue through the node. Such a wavelength routing device can be called a 1xc3x97K wavelength-selective cross connect (WSC), where K is the number of output paths.
One illustrative 1xc3x97K WSC is described in the copending patent application entitled xe2x80x9cINTEGRATED WAVELENGTH ROUTER,xe2x80x9d Ser. No. 10/035,628, filed on Nov. 1, 2001 pending, which is incorporated by reference herein. In that patent application, a WSC is comprised of a demultiplexer arranged to receive an input WDM signal containing N wavelengths, the WDM signal being demultiplexed into N separate wavelengths and applied to a binary tree containing log2K stages of interconnected 1xc3x972 switches. The 1xc3x972 switches can be integrated and have their outputs crossing each other at each stage. The outputs of the final stage are applied to, and combined in, K multiplexers, which provide the K outputs of the WSC.
While the above patent application provides an advancement over prior art arrangements, the crossovers utilized to enable interconnection between each switch stage add loss, crosstalk, and require extra real estate to the implementation of an integrated 1xc3x97K WSC device. Thus, what is desired is an integrated 1xc3x97K WSC device that can be implemented without the use of crossovers.
In accordance with the present invention, an integrated 1xc3x97K WSC apparatus is described that can be implemented with or without the use of crossovers.
More particularly in one embodiment, our integrated 1xc3x97K WSC apparatus comprises
a demultiplexer arranged to couple individual wavelengths in an input optical WDM signal to N respective demultiplexer outputs, where N is an integer greater than one,
a free space region having a left edge and a right edge,
N planar beam steerers arranged along the left edge of the free space region and each connected to a different one of the N demultiplexer outputs,
K waveguide gratings arranged along the right edge of the free space region for multiplexing together multiple light beams received along the right edge of the free space region, where K is an integer greater than one, and wherein
each beam steerer arranged along the left edge of the free space region can selectively direct a light beam from one of the N demultiplexer outputs to a waveguide grating arranged along the right edge of the free space region.